The present invention relates to the art of detection and analysis of analytes using fluorescence. More particularly, the present invention relates to detection of optical signals from multiple biochemical sensors using a photo detection array.
Fluorescence-based biochemical sensors are used to measure many analytes of physiologic interest. For example, fluorescence-based blood analyzers that measure blood gases, electrolytes, metabolites, coagulation state, and immunological markers are commercially available. The ability to measure multiple analytes in parallel is generally useful for the diagnosis of a patient's state of health. This requires an array of biochemical sensors (biosensors) and optical devices to detect the fluorescence from the samples.
Light from an array of biosensors is typically measured using one of the following devices and techniques: dedicated photodetectors, one discrete detector per sensor; a single photodetector, like a photomultiplier, and a scanning light collection system; or a multielement CCD (charge-coupled device) detector. All three approaches have their limitations.
Using one discrete detector per biosensor is costly because each biosensor typically requires a detector, amplifier, and an A/D (analog-to-digital) converter. Therefore, the number and the cost of the components grow proportionally to the number of the biosensors in the array. As the number of components grows, power requirement is increased, system reliability is decreased, and bulk is increased. Using a single detector in combination with a scanning light collection system is mechanically complex and not easily miniaturizable. Using a multielement CCD detector leaves little flexibility in readout of data because the individual elements of the array are not randomly addressable. This may limit the ability to measure signals changing rapidly in time. Further, CCD's suffer from the additional limitation of image blooming, where a saturated pixel leads to charge spill over on adjacent pixels.
Accordingly, there is a need for a technique and an apparatus overcoming these shortcomings of the current art.